The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Truck cabins are often suspended with air spring shock absorber units. As the load in the cabin can vary, and in order to maintain a constant height of the cabin, a mechanical pneumatic valve adds pressure to, or releases pressure from, the air suspension unit. The valve regulates pressure in the air spring unit and thus maintains the truck cabin at a generally constant level, regardless of the load within the cabin.
Typical air spring shock absorbers have included upper and lower assemblies, with a shock absorber-like component coupled between the two assemblies. Typically, a flexible bladder-like member encloses the shock absorber like element within an enclosed area. The upper assembly is typically coupled to the cabin, and the lower assembly is coupled to a frame portion of the vehicle. The air spring unit thus supports the cabin above the frame portion of the vehicle in a manner that permits the height of the cabin to be adjusted, depending on the load in the cabin. During operation of the vehicle, at least some small degree of tilting or torsional movement of the upper assembly relative to the lower assembly can be experienced.
In general, with traditional air spring shock absorber units, the valve that is used to control the height of the cabin has typically been located remotely from the air spring shock absorber unit. However, more recently, mechanisms have become available to integrate the valve into the internal construction of the air spring shock absorber. A major challenge to overcome with such an internally mounted valve is the mechanism which is needed to physically actuate the internally mounted valve. More specifically, the challenge is with integrating the component which physically actuates the valve into the interior area of the shock absorber unit. This has proved quite difficult for a number of reasons. For one, the actuating member has to be able move generally linearly with the upper assembly as the upper assembly moves towards and away from the lower assembly. This is needed so that the internal valve's opening and closing is directly linked to the cabin height. However, when attaching the actuating member directly to the upper assembly, the actuating member itself now becomes subject to the tilting and torsional movements of the upper assembly, relative to the lower assembly, as the cabin moves about while the vehicle is in motion. The tilting and torsional movements of the cabin, however, are problematic if the actuating member is directly tied to the upper assembly (which is directly supporting the cabin) as these movements can cause repeated bending and twisting of the actuating member. Accordingly, the significant challenge has been how to integrate the actuating member into the interior area of an air spring shock absorber so that it is able to sense the vertical movement of the upper assembly relative to the lower assembly, without being significantly affected by the tilting and torsional movements of the upper assembly relative to the lower assembly.